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[photo-3d] Re: 2x2x2 projection
- From: JNorman805@xxxxxxx
- Subject: [photo-3d] Re: 2x2x2 projection
- Date: Fri, 6 Apr 2001 12:04:45 EDT
Bruce the Recumbent writes:
> <<Must have been off-list response.>>
Yes, I think it was.
<< What reasoning did the explainers use?>>
I got a response from one person who said he had acquired 2x2x2 slide pairs
already mounted, and that the spacer between them was 1/2 inch.
<<> Is that projector made to successfully project 8P slides in a
> Realist-sized stereo mount?>>
Dunno, never tried 8p (except vertically, of course).
<<> Maybe a 2x2x2 horizontal shooter who doesn't feel like remounting in
> stereo slides for a TDC show would find your invention nice. Is this
> spacer attached to the 2x2's, or just loose between them somehow? What
> should it be made of? If the coverage of the projector is adequate for
> the full vertical image, I guess it would be for the horizontal as well,
> and I'd expect the same spacer size to apply, since the slide is the same
> width as height, and the aperture is centered in the slide both vertically
> and horizontally. Are all these assumptions true? >>
Here's what I did: First, I centered the vertically oriented 2x2 slides over
the openings in a realist mount, then measured the distance between the edges
of the two slides. It was 3/8 inch. That didn't work; horrendous vignetting
at the upper and lower left corners. Then I followed the 1/2 inch advice.
Still didn't work, although there was less vignetting. Then I tried 5/8
inch. Bingo!
Here's how I did it: First, I cut a 1 3/8 x 1 7/8 inch rectangle from heavy
card stock (probably the equivalent of 3 or 4 thicknesses of index card),
using a rotatrim cutter to make sure everything was squared up. Then I
covered one side of the card stock with double sided tape. Then I placed the
short edge of the piece of card stock (tape side up) against the graduated
straight edge of the rotatrimmer, with one corner at a convenient inch mark.
Then, using the straight edge as a stop and a guide, I placed the right side
slide over the taped card stock so that the left edge of the slide covered
3/8 inch of the taped surface. The slide was right side up, so that the top
of the slide was against the straight edge, and the bottom extended 1/8 below
the 1 7/8 dimension of the taped card stock. (This is important, because
when you project you will turn the assemblage upside down, and you will want
the edge of the whole thing to glide smoothly along the bottom of the carrier
channel.) Next, I cut a 5/8 x 1 7/8 rectangle from the same card stock
material, and pressed that dlown onto the taped surface of the other piece of
card, right next to the slide that was already taped there. Finally,
applying finger pressure to keep the whole thing firmly pressed against the
straight edge, I laid the second slide next to the 5/8 inch spacer. That's
all there is to it. Bearing in mind that the vignetting is caused by the
edge of the circle of projected light, and noting that the openings in the
slide carrier are square (you know, like the screen should be?), my guess is
that if the 5/8-inch spacer eliminates the vignetting at the top and bottom
corners it will also allow the circle of light to extend past the outer edge
of a slide lying on its side, i.e., horizontal. But I don't know for sure,
so you'll just have to try it. (Does anyone else know if the openings in the
carrier of the TDC 116 need to be widened to accommodate 8P horizontally?
Dr. T?) You may have to make the backing card narrower than 1 3/8 inch to
avoid having that 3/8 overlap cutting into the image area, since the edges of
the mount are narrower on the horizontal orientation of the slide. Also,
bear in mind that what I did works for my TDC 116. I have no idea if it will
work for anyone else's projector.
Note for Bruce and any other APECers reading this: If you still have any of
my APEC cards and haven't given them the old heave ho because they don't fit
with the true Holmes size cards in your collection, the card stock that I
used to mount them on is the same as what I used for this little project.
Jim the Ab (It's funny, my friends in college used to call me "Ab" as a
nickname)
[Non-text portions of this message have been removed]
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